The inventive concept relates generally to nonvolatile memory device comprising variable resistance memory cells, and related methods of operation.
Some memory devices store information using variable resistance materials. Such devices may be referred to generally as variable resistance memory devices. Examples of such devices include phase-change random access memories (PRAMs), resistive RAMs (RRAMs), and magnetic RAMs (MRAMs).
In a typical variable resistance memory device, information is stored by changing a storage element from a first resistance state (e.g., low resistance) corresponding to a first data value (e.g., a “1”) to a second resistance state (e.g., high resistance) corresponding to a second data value (e.g., a “0”). For example, in a PRAM, information is stored by applying electrical current to a phase-change material such as chalcogenide to change it from a crystalline state (or “set” state) of relatively high resistance to an amorphous state (or “reset” state) of relatively low resistance, or vice versa. In the PRAM, the electrical current is used to heat and then cool the phase-change material such that it assumes either the set state or the reset state.
In some variable resistance memory devices, memory cells share a virtual address space with other components, such as registers, buffers, or other memories. The memory cells may have different access latency compared to the other components, so the timing of a read or write command may depend on whether the corresponding virtual address designates memory cells or some other components.